JP2820298B2 - Austenitic stainless steel sheet manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an austenitic stainless steel sheet manufacturing apparatus, and particularly to a so-called synchronous continuous casting process in which there is no relative speed difference between a slab and an inner wall surface of a mold. The present invention relates to an apparatus for producing an austenitic stainless steel sheet by cold rolling a slab having a thickness close to the thickness of a cast product.

[Conventional technology]

The conventional method of manufacturing a stainless steel sheet using a continuous casting method has a thickness of 100 mm while vibrating the mold to the casting method.
Cast into the above slabs, clean the surface of the resulting slabs, and after heating in a heating furnace to 1000 ℃ or more, subjected to hot rolling by a hot strip mill consisting of a row of rough rolling mills and finishing mills A hot strip with a thickness of several mm
Furthermore, after annealing as required, descaling and cold rolling were performed to perform final annealing.

As described above, in the conventional process, a long hot strip mill is required for hot rolling a slab having a thickness of 100 mm or more, and a large amount of energy is used for heating and rolling the slab. was there.

In order to solve this problem, research is being conducted on a process for producing a slab having a thickness equal to or close to that of a hot strip by continuous casting. For example, the twin-roll method, twin-belt method, etc., such as those introduced in the papers featured in “Iron and Steel” '85 -A197 to '85 -A256, show the relative speed difference between the slab and the inner wall of the mold. There is no synchronous continuous casting process.

That is, as a first method of the continuous casting process, a thin cast slab having a thickness of 0.5 to 10 mm is obtained in advance by the twin roll method, and thereafter, an annealing step and a pickling step for scale removal are performed. There is a method of manufacturing a sheet product having a predetermined thickness only by rolling.

As a second method of the continuous casting process, a thin cast slab having a thickness of 0.5 to 10 mm is obtained in advance by the twin-roll method, then subjected to hot rolling, scale is removed by pickling, and then cold-rolled. There is known a method of manufacturing a thin plate product having a predetermined thickness.

[Problems to be solved by the invention]

However, in the above-mentioned conventional method, in order to obtain a cold-rolled sheet product having a good metal grain structure and a good surface quality in a slab state, it is necessary to considerably increase the cold-rolling rate particularly in the first method. In the second method, it is necessary to perform hot rolling before cold rolling. Therefore, there have been problems such as a long manufacturing time and a remarkable increase in cost.

An object of the present invention is to provide an austenitic stainless steel sheet manufacturing apparatus in which the occurrence of minute irregularities, undulations (roping) and uneven gloss is reduced on the surface.

[Means for solving the problem]

According to the present invention, there is provided a twin-roll caster including a pair of opposed cooling rolls for casting austenitic (γ) stainless steel molten steel, and (b) a thin cast slab obtained by the twin-roll caster. To 12
(C) a slab heated by the heating device to 1200 ° C.
A cooling device for cooling below, wherein at least one set of the heating device and the cooling device are alternately arranged, and the apparatus for producing an austenitic stainless steel sheet is solved.

It is preferable to include a device for applying plastic deformation to the thin cast slab as a pre-process of the heating device.

Note that the twin-roll type thin plate casting apparatus referred to here does not depend on the direction in which the slab is drawn. Further, both roll diameters do not necessarily have to be the same. That is, it includes a vertical type, an inclined type twin roll caster, and a different roll diameter twin roll caster.

[Function] FIG. 7 is a ternary phase diagram (Fe30% vertical sectional view) of Fe—Cr—Ni for explaining the phase transformation of SUS304 according to the present invention.

In the present invention, the austenitic (γ) stainless thin cast slab obtained in the continuous casting process by the twin roll method is heated to 1200 ° C. or more and 1450 ° C. or less, and the δ + γ two-phase state Y or δ
After maintaining in the one-phase state Z, cooling and performing a heat treatment for returning to the γ-phase state X one or more times to cause a δ / γ transformation action, and also to rework by performing plastic working such as rolling. The metal crystals are refined by the transformation promoting action.

As described above, by subjecting the material having the metal crystal grains refined by the heat treatment and plastic working of the present invention to final rolling, the surface properties such as roping and uneven gloss of the cold rolled sheet are improved.

In the present invention, austenitic stainless steel is used as the target material. That is, SUS304, SUS316, SUS303 and the like are favorably used.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings along with a conventional example and a comparative example.

FIG. 1 is a schematic sectional view of a twin-roll caster used in the method of this embodiment.

The two rolls (1, 2) facing each other in FIG.
It is made of water-cooled copper alloy with a width of 0 cm and a width of 10 cm. The rolls 1 and 2 have a rotary drive device (not shown) using an electric motor and a slab pressing device 3 using a spring. By controlling the roll rotation speed and the roll interval, a thin cast piece 7 having a desired plate thickness can be cast. The molten steel pool 4 is held by pressing a side dam 5 made of a refractory plate facing the rotating roll side surface. 6 is a solidified shell. The slab 7 made of twin rolls is applied to the casting line of FIG. 2 showing the first embodiment or the casting line of FIG. 3 showing the second embodiment.

In this embodiment, the component: 18Cr-8Ni austenitic stainless steel (SUS304) using the twin roll casting machine, casting temperature: 1510 ° C., roll rotation speed: 1.4 m / sec, plate thickness: 1.0 mm,
A thin cast slab having a width of 100 mm was produced. In the first embodiment shown in FIG. 2, a slab 7 made of twin rolls first enters a heating device 8 immediately below the roll, and is passed through a cooling device 9 to a conventional winding device 10 and a cooling device. The heating device directly below the roll of this embodiment uses a high-frequency heating device or a burner,
The thin cast slab 7 is controlled to be heated to 1450 ° C. or more and 1450 ° C. or less. As the cooling device 9, a device for forcibly cooling the slab 7 to 1200 ° C. or lower by gas cooling is used. In the second embodiment shown in FIG. 3, after the heating device 8 of the above embodiment, a light working device 11 for cooling and working, a heating device 12, and a cooling device 9 are provided. Table 2 shows the results (average γ particle size, roping height, and uneven gloss) of the comparative material not subjected to the heat treatment and the material subjected to the heat treatments A and B, respectively. FIG. 4 shows heat treatment curves of the comparative material (conventional example) and heat treatments A and B. Heat treatment A corresponds to the first embodiment, and heat treatment B corresponds to the second embodiment.

5 and 6 are metallographic photographs of a comparative material (conventional example) and a material subjected to heat treatment A, respectively. From this photograph, it can be seen that the material subjected to the heat treatment A has clearly refined crystal grains as compared with the comparative material (refinement of the average γ grain size).
It can also be seen that the roping height and gloss unevenness are much improved compared to the comparative material (conventional example). In the heat treatments A and B in Table 2, the cooling temperature is about 800 to 1200 ° C.

〔The invention's effect〕

As described above, according to the present invention, it is possible to manufacture a cold rolled sheet having a more beautiful skin than the conventional one by using a twin-roll type thin sheet casting method, in which minute irregularities, undulations (roping) and uneven gloss on the surface of a thin sheet product are significantly reduced. Become.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a twin-roll caster used in the method of the present embodiment. FIGS. 2 and 3 show the casting lines of the first and second embodiments according to the present invention, respectively. FIG. 4 is a schematic view, and FIG. 4 shows heat treatment curves of a comparative material and heat treatments A and B, respectively.
Fig. 7 is a ternary phase diagram (Fe30% vertical sectional view) of Fe-Cr-Ni for explaining the phase transformation (δ / γ transformation) of SUS304 according to the present invention. ). 1,2: twin rolls, 3: slab squeezing device, 4: molten steel pool, 5: side dam (cough), 6: solidified shell, 7: thin slab, 8,12: heating device , 9 ... cooling device, 10 ... winding device, 11 ... light processing device.

──────────────────────────────────────────────────の Continuation of front page (72) Inventor Kenichi Miyazawa 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Corporation Kimitsu Works (56) References JP-A-3-42145 (JP, A) JP 63-115654 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22D 11/06 330 B22D 11/00 C21D 9/46

Claims (2)

(57) [Claims] 1. A twin roll caster comprising a pair of opposed cooling rolls for casting austenitic (γ) stainless steel molten steel, and b) a thin cast slab obtained by the twin roll caster is
(C) a slab heated by the heating device to 1200 ° C.
An austenitic stainless steel sheet manufacturing apparatus, comprising: a cooling device for cooling below, wherein at least one set of the heating device and the cooling device are alternately arranged. 2. The apparatus according to claim 1, further comprising an apparatus for applying a plastic deformation to the thin cast slab as a pre-process of the heating apparatus.